Irrigation systems such as center pivot systems have a structure from which down tube are suspended, with sprinkler heads attached to the down tubes. The sprinkler heads take a number of different forms and all try to create a uniform and random spread of water droplets, or a size which does not result in excessive evaporation. The sprinkling heads may also be mounted on top of the rotating structures of the center pivot systems, or on upward turned ends of the down tubes. Such sprinkler heads can operate in any orientation, because the force of the water stream is greater than the force of gravity on the lightweight sprinkler parts. However, for convenience the sprinkler head and its parts are described as being in the orientation as shown in the figures, with “upper”, “lower”, “top”, and “bottom” surfaces applied to the sprinkler parts in the orientation shown in the figures.
A large and uniform spray of water is preferable, so that the areas watered by a particular sprinkler head overlap with neighboring sprinkler head, and the ground under the sprinklers is uniformly covered.